The present invention is directed to silicone acrylate containing acrylic-based emulsion pressure-sensitive adhesives which are initially repositionable, become permanent with age and display water resistance.
The concern over the environment has made pressure-sensitive adhesive polymers formed by emulsion or bulk polymerization, as opposed to polymerization in organic solvents attractive. Emulsion polymers can be coated onto a substrate, e.g. face material, release liner, and/or a transfer surface, and a pressure-sensitive adhesive layer formed upon water evaporation.
The possibility of preparing a pressure-sensitive adhesive in an emulsion has been mentioned in the art. Examples include U.S. Pat. No. 3,637,615 to Coffman, U.S. Pat. No. 4,069,123 to Skoultchi et al and U.S. Pat. No. 4,185,050 to Lazear et al.
While the possibility of preparing emulsion pressure-sensitive adhesives has been mentioned, the art in exemplifying the best mode of invention has adhered to the preparation of pressure-sensitive adhesive polymers in an organic solvent. The reason may be the fact that the quality of the emulsion adhesives was poor and the emulsion-based pressure-sensitive adhesives were more of a curiosity than a way to eliminate the organic solvent.
Emulsion-based pressure-sensitive adhesives have been found, as compared to solvent-based adhesives, to generally have deficient performance properties in certain respects, such as water resistance. The present invention is directed to emulsion polymers which overcome the deficiencies of the prior art emulsion polymers.